This invention relates to a vehicular-mounted plow for clearing snow and the like, and more particularly, to a ram actuated snowplow. The invention more specifically involves a vehicular-mounted plow having a locking mechanism which permits the plow moldboard to be selectively repositioned when necessary, and also acts to protect the ram from the stresses of plowing.
In one type of hydraulically actuated assembly, a drive frame is secured to the front of a motor vehicle and pivotably supports a moldboard unit so that it can swing from one side of the vehicle to the other. A pair of hydraulic reversing rams are mounted on either side of the frame which have extendable rods attached to the moldboard unit on either side of the pivot point. The rams are selectively controlled by an operator stationed in the cab of the vehicle to position the moldboard at a desired plowing angle. In operation one ram extends while the other retracts to set the moldboard at a desired angle. Once set, the cylinders are required to hold the moldboard in position during the plowing operation. As a consequence, plowing stresses are translated directly to the power rams which in turn, results in worn piston seals, bent drive rods and failures in other cylinder related components.
Another type of reversing mechanism that has been widely used in the industry is a worm-gear mechanism in which a sector gear is secured to a moldboard unit and is rotated by a motor driven pinion mounted on the support frame. In this type of mechanism there is no power ram, so problems such as worn piston seals and bent piston rods are avoided. However, relatively large stresses can be transmitted from the moldboard to the worm-gear and drive motor which again can cause damage to the drive mechanism.
A locking/release mechanism for a reversable plow assembly is described in U.S. Pat. No. 4,215,494. In this assembly, a ram actuated, vehicular-mounted, snowplow is disclosed having a sector plate mounted on a lifting frame and has a coacting rocker arm mounted on a rotatable drive frame. Raising the lift frame of the plow causes the rocker arm to be released from the sector plate so that the moldboard angle can be changed when the plow is raised. The rocker arm is reengaged with the sector plate when the moldboard is again lowered. This arrangement does have several advantages over the devices previously discussed, however, the operator must raise the plow prior to reversing the blade, and then must thereafter lower the plow. This involves three separate operations which is time consuming and places undue wear on the lifting mechanism.